lundi 16 février 2015

Rosetta - Close encounter

ESA - Rosetta Mission patch.

16 February 2015

Comet on 14 February from 8.7 km

On 14 February 2015, Rosetta swooped over the surface of Comet 67P/Churyumov–Gerasimenko at a distance of just 6 km. The closest approach took place at 12:41 GMT over a region known as Imhotep, which is on the larger of the comet’s two lobes.

The image reveals the contrasting terrains seen on this comet. Layered and fractured exposed surfaces contrast against expanses of smooth, dust-covered terrain. In some places, such as to the lower right of this image, the faint outline of raised near-circular objects with smooth surfaces can be seen. Elsewhere, boulders ranging in size from a few metres to a few tens of metres are scattered across the surface. The largest boulder, seen to the upper right, is named Cheops.

14 February close flyby, 10:15 GMT

Images above: Four-image montage of Comet 67P/Churyumov–Gerasimenko comprising images taken on 14 February 2015 during the first dedicated close flyby. This image set was taken at 10:32 GMT from a distance of 12.6 km from the comet centre, or about 10.6 km from the surface seen in the foreground. Using the surface distance, the image scale is 0.9 m/pixel and the montage measures about 1.8 km across.

As well as providing the opportunity to take close-up high-resolution images of the surface, flybys like this also allow Rosetta’s instruments to sample the innermost parts of the comet’s atmosphere, or coma, to understand the connection between the source of the observed activity and the wider coma.

The spacecraft has now begun a new phase of observations, whereby it will continue to fly past at a range of distances, typically between about 15 km and 100 km.

The more distant flybys will provide the broader context of a wide-angle view of the nucleus and its growing coma as the comet moves towards perihelion – the closest approach to the Sun along its orbit. Rosetta is today 345 million kilometres from the Sun; at perihelion, on 13 August this year, it will be at about 186 million kilometres, between the orbits of Earth and Mars.

14 February close flyby, 19:42 GMT

Images above: Four-image montage of Comet 67P/Churyumov–Gerasimenko comprising images taken on 14 February 2015 during the first dedicated close flyby. This set was taken at 19:42 GMT from a distance of 31.6 km from the comet centre. The image scale is 2.7 m/pixel and the montage measures 5.5 km across.

The image presented here was taken with the navigation camera shortly after closest approach, at 14:19 GMT, from a distance of 8.7 km. It has a scale of 0.74 m/pixel and measures 0.76 km across.